if your site dont have good page rank, the only way is to drive more traffic to it. In the mean time, you can try google adsense, bidvertiser and adbrite to earn some money. You can also join affiliate program like clickbank, and shoppingads. Even some of the pay to review and post site will accept your blog like blogvertise and sponsoredreviews. The last thing you can try is put those Pay per impression program ads like the news room. Hope it helps!